Mesenchymal Stromal Cell-derived Extracellular Vesicles in Preclinical Animal Models of Tumor Growth: Systematic Review and Meta-analysis.

BACKGROUND: Mesenchymal stromal cell derived extracellular vesicles (MSC-EVs) have been implicated in the regulation of tumor growth. Studies remain preclinical with effects ranging from inhibition of tumor growth to cancer progression. A systematic review and meta-analysis is needed to clarify the effect of MSC-EVs on tumor growth to facilitate potential translation to clinical trials. METHODS: A systematic search of the literature (MEDLINE, Embase, and BIOSIS databases to June 1, 2019) identified all pre-clinical controlled studies investigating the effect of MSC-EVs on tumor growth. Study selection and data extraction were performed in duplicate. Potential risk of bias was assessed using the SYRCLE tool. A random effects meta-analysis of reduction in tumor weight/volume (primary outcome) was performed. RESULTS: We identified 29 articles and 22 reported data on tumor responses that were included for meta-analysis. Studies were associated with unclear risk of bias in a large proportion of domains in accordance with the SYRCLE tool for determining risk of bias in preclinical studies. A high risk of bias was not identified in any study. MSC-EVs had a mixed response on tumor progression with some studies reporting inhibition of tumor growth and others reporting tumor progression. Overall, MSC-EVs exerted a non-significant reduction in tumor growth compared to controls (standardized mean difference (SMD) -0.80, 95 % CI -1.64 to 0.03, p = 0.06, I2 = 87 %). Some studies reported increased tumor growth which aligned with their stated hypothesis and some interrogated mechanisms in cancer biology. EVs isolated from MSCs that overexpressed anti-tumor RNAs were associated with significant tumor reduction in meta-analysis (SMD - 2.40, 95 % CI -3.36 to -1.44, p < 0.001). Heterogeneity between studies was observed and included aspects of study design such as enrichment of MSC-EVs with specific anti-tumor molecules, tissue source of MSCs, method of EV isolation, characterization of MSCs and EVs, dosage and administration schedules, and tissue type and source of tumor cells studied. CONCLUSIONS: MSC-EVs are associated with mixed effects on tumor growth in animal models of cancer. In studies where anti-tumor RNAs are packaged in EVs, a significant reduction in tumor growth was observed. Reducing heterogeneity in study design may accelerate our understanding of the potential effects of MSC-EVs on cancer. [274 words] Forest plot of MSC-EV effect on tumor growth accordinggenetic modification of EVs in animal studies identified from a systematicreview of the literature. All cohorts from studies with multiple interventiongroups are presented separately with control groups divided equally among thegroups. M, modified; H, hypoxia.

The Effects of Essential and Non-Essential Metal Toxicity in the Drosophila melanogaster Insect Model: A Review.

The biological effects of environmental metal contamination are important issues in an industrialized, resource-dependent world. Different metals have different roles in biology and can be classified as essential if they are required by a living organism (e.g., as cofactors), or as non-essential metals if they are not. While essential metal ions have been well studied in many eukaryotic species, less is known about the effects of non-essential metals, even though essential and non-essential metals are often chemically similar and can bind to the same biological ligands. Insects are often exposed to a variety of contaminated environments and associated essential and non-essential metal toxicity, but many questions regarding their response to toxicity remain unanswered. Drosophila melanogaster is an excellent insect model species in which to study the effects of toxic metal due to the extensive experimental and genetic resources available for this species. Here, we review the current understanding of the impact of a suite of essential and non-essential metals (Cu, Fe, Zn, Hg, Pb, Cd, and Ni) on the D. melanogaster metal response system, highlighting the knowledge gaps between essential and non-essential metals in D. melanogaster. This review emphasizes the need to use multiple metals, multiple genetic backgrounds, and both sexes in future studies to help guide future research towards better understanding the effects of metal contamination in general.

Impact of Exercise Training on Hematological Outcomes Following Hematopoietic Cell Transplantation: A Scoping Review.

PURPOSE: Hematopoietic cell transplantation (HCT) is associated with significant risk prior to hematopoietic engraftment. Endurance exercise can modify the bone marrow microenvironment, alter hematopoiesis and accelerate hematopoietic regeneration in mouse models of transplantation. METHODS: A systematic review was conducted to clarify the impact of exercise on clinically relevant hemato-logical outcomes in patients following HCT. RESULTS: A systematic search of the literature identified 13 studies (total of 615 participants; 313 in study arms). Studies included exercise regimens that were primarily low-to-moderate intensity. A total of five studies re-ported on engraftment and length of stay, which were largely unchanged with intervention. Rates of graft-ver-sus host disease were reported in six studies whereas red cell and platelet transfusion needs were reported in four studies, neither of which was different with exercise. Survival was reported in four studies and was significantly improved by exercise in one study. CONCLUSIONS: Exercise in patients receiving HCT appears feasible and safe. Heterogeneity in type and intensity of exercise was observed and few studies examined high intensity exercise. Outcome reporting was inconsis-tent regarding transplant-related outcomes. Standardized hematological outcome measures are needed to clarify the impact of higher intensity exercise on HCT.

Preclinical Studies of MSC-Derived Extracellular Vesicles to Treat or Prevent Graft Versus Host Disease: a Systematic Review of the Literature.

INTRODUCTION: Treating and preventing graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplant (HCT) remains a significant challenge. The use of mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) appears promising and a systematic review of preclinical studies is needed to accelerate the design of translational studies. METHODS: We identified 4 eligible studies from a systematic review performed on December 1, 2018. In brief, eligible studies included the treatment or prevention of GVHD in animal models and the use of MSC-EVs. Study design and outcome data were extracted and reporting was evaluated using the SYRCLE tool to identify potential bias. RESULTS: Two studies assessed the efficacy of MSC-EVs in treatment of GVHD and 2 studies address prevention. Mice treated with MSC-EVs showed improved median survival, GVHD clinical scores and histology scores as compared to untreated mice with GVHD. Prophylactic treatment with MSC-EVs attenuated GVHD severity and improved median survival as compared to no treatment or saline. CONCLUSION: Our systematic review provides important insight regarding the potential of MSC-EVs to treat or prevent GVHD. Although few studies were identified, improved survival and attenuated histologic findings of GVHD were observed in mice after MSC-EV administration for the treatment and prevention of GVHD. Dosing of EVs and route of administration remain inconsistent, however, and scalability of EV isolation for clinical studies remains a challenge. Standardized outcome reporting is needed to pool results for metanalysis. Graphical abstract.

An Analysis of Mesenchymal Stem Cell-Derived Extracellular Vesicles for Preclinical Use.

Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) can reduce inflammation, promote healing, and improve organ function, thereby providing a potential "cell-free" therapy. Prior to clinical translation, it is critical to synthesize existing evidence on preclinical methods and efficacy. To address these issues, we used gold standard systematic review methodology to consolidate information from all published animal studies investigating MSC-EVs as an intervention. A systematic search of MEDLINE and Embase identified 206 studies. Data were extracted in duplicate for methodology, experimental design, interventional traits, modifications, and outcomes. MSC-EVs were used to treat a variety of diseases and demonstrated benefits in 97% of studies. Adverse effects were reported in only three studies, two demonstrating tumor growth. A quarter of articles modified EVs to enhance efficacy, with 72% leading to markedly improved outcomes as compared to unmodified EVs. However, several key methodological concerns were evident. Only 60% of studies used nomenclature consistent with the size definitions of EVs. Ultracentrifugation (70%) and isolation kits (23%) were the most common isolation techniques with noted differences in yield and purity. EVs were inconsistently dosed by protein (68%) or particle concentration (16%). Two-thirds of studies administered xenogeneic EVs, suggesting immunocompatibility. Less than 25% of studies assessed EV biodistribution. Approaches for determining size, protein markers, and morphology were highly heterogeneous, with only 12 and 4 studies meeting the MISEV 2014 and 2018 recommendations, respectively. Knowledge gaps identified from this systematic review highlight important opportunities to improve preclinical design and methodology in the rapidly growing field of EV therapeutics.

Methods and efficacy of extracellular vesicles derived from mesenchymal stromal cells in animal models of disease: a preclinical systematic review protocol.

BACKGROUND: Over the past decade, mesenchymal stromal cells have been increasingly investigated for their therapeutic potential in several different illnesses. However, cell therapy can be limited by potentially serious adverse events including cell embolus formation and tumorigenesis. Importantly, the protective effects of mesenchymal stromal cells are largely mediated by paracrine mechanisms including release of extracellular vesicles. This systematic review intends to synthesize the current knowledge of mesenchymal stromal cell-derived extracellular vesicles as a therapeutic option for preclinical models of disease, inflammation, or injury. METHODS: A systematic literature search of MEDLINE, Embase, and BIOSIS databases will be conducted. Interventional preclinical in vivo studies using extracellular vesicles derived from any tissue source of mesenchymal stromal cells will be included. Studies will be screened by abstract, and full-text by two independent reviewers. Eligible studies will undergo data extraction with subcategorization into domains based on disease. Methods utilized for extracellular vesicle characterization and isolation will be collected, as well as information on interventional traits, such as tissue source of mesenchymal stromal cells, dosage regimen, and vesicle modifications. Reported outcomes will be collected to determine which diseases studied may be impacted most from treatment with mesenchymal stromal cell-derived extracellular vesicles. DISCUSSION: This systematic review will summarize preclinical studies investigating the therapeutic efficacy of both small and large extracellular vesicles derived by mesenchymal stromal cells. Extracellular vesicles represent a possibility to harness the benefits of mesenchymal stromal cells with added benefits of reduced manufacturing costs and an improved safety profile. Hence, there has been an exponential increase in interest for developing this cell-free therapy with hundreds of preclinical studies published to date. However, a vast amount of heterogeneity between groups relates to methods of extracellular vesicle isolation, characterization, and study design. This review will capture this heterogeneity and identify the most commonly used and optimal approaches to evaluate mesenchymal stromal cell-derived extracellular vesicle treatment. A meta-analysis of outcomes within each disease domain will help elucidate which fields of research demonstrate promise for developing extracellular vesicles as a novel cell-free therapy. Summarizing this robust information on extracellular vesicles as an intervention can provide guidance for designing preclinical studies with hopes of future clinical translation.